Polyurethane-based coatings which are curable at ambient temperatures have been developed. Such polyurethane based coatings are not produced with the use of isocyanates. Rather, a polycarbamate is crosslinked with a polyaldehyde in the presence of an acid catalyst to form a crosslinked polyurethane coating, herein called a “non-isocyanate polyurethane coating.” When used with typical epoxy primers or mid-coats, non-isocyanate polyurethane-based topcoats may show decreased performance in comparison to such topcoats placed on unprimed substrates. A primer and/or midcoat coating layer which does not exhibit such decreased performance would be useful.